I'm the worst. I just leave the bag in for 20, cut it, and dump the whole deal in there. I must be lucky.
That's what I do and I've never had any issues with it. Now granted I only buy fish from my trusted LFS's that all have high water standards.
Still I think this fanaticism with waiting any longer than 20-30min with bag in water to introduce fish is not taking the fish in the actual bag into account.
-A cycled aquarium already is able to readily break down any ammonia in the LFS bag water
-If anything the LFS bag water upon entering tank will help the new fish acclimate to your tank better, not the opposite. To think the opposite is true is actually the illogical assumption if you think about it (at least to me)
I believe the fanaticism that has created the hour-long mandated processes is the assumption that all fish are coming from Petsmart or big chains full of ICK. I believe that's a naive assumption. The hobby has matured. The LFS's I buy from all have near religious water standards and or years old filtration systems full of trillions of BB. The idea that you can't trust your LFS is, I believe, actually if anything causing fish more stress. Who buys fish from a place with dead fish in the tanks? Who buys fish without checking all the tanks in the store first?
It just seems people have reached a fanaticism esq level purely based on hypotheticals which if you're doing your due diligence do not apply.